Most specimens of M. yongmunensis possess several stromata (up to 10), on a large pupa of Lepidoptera deeply buried in soil. Stroma of the species is typically branched in a dichotomous way at its basal or upper regions. Perithecia are usually obliquely inserted in the stromata with a few exceptions that are ordinally arranged, i.e. at right angles to the surface of the stromata. While some perithecia are characterized by an acute narrowing of the perithecium at the ostiole, producing a narrow terminal end, others are not significantly narrowed. In the asci the ascospores are arranged parallel for their entire length and almost reach the ascus foot, suggesting that ascospores are of approximately the same length as the asci. Unlike the distinct septation of ascospores as seen in C. militaris, the septa of the ascospores are indistinct and discharged ascospores do not disarticulate into part-spores. In the anamorph of M. yongmunensis, cultures derived from ascospores are moderately fast growing in SDAY (Sabouraud-dextrose-yeast extract agar) and the colonies reach 25–35 mm diam at 25 °C in 10 d. Colonies are slightly cottony without zonation and white with a green margin, remaining greenish brown at the reverse side of the cultures. Conidiophores are erect and produced in prostrate aerial hyphae. Phialides are solitary, not in whorls, broader at the base and tapering towards the end, measuring 20–28 × 2.0–2.2 µm. Conidia are in slimy heads (with usually 2 or 3 conidia) and ellipsoidal to oblong, measuring 2–3.5 × 1.5–2.4 µm. In submerged areas of the cultures, chlamydospores are developed in chains or reduced to intercalary swollen structures. The anamorph of M.yongmunensis is best classified as pochonia-like because of its subulate phialides and
production of chlamydospores, although verticillium-like whorls of phialides were not observed. In Metacordyceps, M. yongmunensis is most similar to M. chlamydosporia (= C. chlamydosporia) in the shape of perithecia and its anamorph. Both species produce brownish perithecia that possess long terminal ends in white or pale yellow stromata. The anamorph of M. chlamydosporia is identical with the type of Pochonia. Thus the production of chlamydospores can be informative for recognizing some species of Metacordyceps.